This invention relates to a process of gasifying fuel which is mainly in the form of lumps under a pressure of about 5 to 150 bars in a water-cooled double-walled reactor chamber, which is provided at its upper end with a feeder for the fuel to be gasified and at its lower end with a rotary grate, through which the incombustible residue of the fuel, the so-called ash, is withdrawn from the reaction chamber and the gasifying agent consisting of free oxygen-containing gases as well as water vapor and/or carbon dioxide is distributed over the cross-section of the shaft and in this distribution is fed into the reactor chamber to flow therein opposite to the coal or other solid fuel, whereas the product gas, which contains water vapor, hydrocarbons, and dust, is withdrawn from the upper portion of the reactor at a temperature between about 350.degree. and 800.degree. C, and the ash is removed from the reactor chamber at a temperature above about 250.degree. C through the rotary grate. The feeding of the solid material and the discharge of the incombustible residue into and out of spaces which are under superatmospheric pressure are effected through known lock chambers.
It has been known for decades that solid fuels such as hard coal, brown coal and peat, can be gasified under superatmospheric pressure. Details of the process have been described, e.g., in the U.S. Pat. No. 2,667,409;
German Pat. No. 1,021,116, and German specifications DOS Nos. 2,346,833; 2,351,963; and 2,353,241. Gasification reactors of this kind are known in the art as LURGI Pressure Gas Producers. The gasification of solid fuels under superatmospheric pressure on a large scale in a process which has proved satisfactory is gaining in importance in view of an increasing shortage of energy resources, particularly as far as liquid and gaseous fuel reserves are concerned. Because the gas produced by a treatment of solid fuel with gasifying agents consisting of technically pure oxygen and water vapor consists in a considerable part of hydrogen, carbon oxides and methane, it can be used as a starting product for various syntheses. A mixture of free oxygen-containing gases, such as air or oxygen-enriched air, and superheated steam, can be used for a treatment by which so-called lean or dilute gases having a relatively low heating value of about 1200 to 2000 kcal per standard m.sup.3 of dry gas can be produced. Such gases are particularly suitable as fuel for heating plants and for power plants, e.g., combined gas turbine-steam turbine power plants.